Pressure-actuated valve

ABSTRACT

A pressure-actuated relief valve is disclosed having biasing means urging the poppet to a closed position which biasing means includes a damped and an undamped member cooperating to provide fast response while controlling poppet oscillation. The damped member includes a spring within a hydraulic dashpot and serves as a reaction seat for the undamped member. Fast pressure increases compress only the undamped member while longer duration pressure signals will also compress the damped member.

States Patent Inventor Alexander 2,518.387 8/l950 Shaw 137/5145Hulchmson, Kans- 2,686,534 8 1954 Montelius. 137/514 PP 379,8163,054,420 9/1962 Williams. l37/469 Flled 1969 3.l30.748 4/1964Weingartner. 137/514 51 Patented N v- 23, 1971 3.370.601 2 1968 Nevulis137/87 73 Assi nee The Cessna Aircraft Co i 8 Wichita K mpany PrimaryExaminer-Laverne D. Geiger Asxislam Examiner-William H. WrightAttorneys-Gregry J. Nelson. James W. McFarland and 541 PRESSURE-ACTUATEDVALVE Mi1lr& Brown 7 Claims, 1 Drawing Fig.

L- 137/514 ABSTRACT: A pressure-actuated relief valve is disclosed hav-[51] lint. Cl ..F16k 21/06, ing biasing means urging the poppet to aclosed position which F fik 7/02 biasing means includes a damped and anundamped member [50] Field of Search 137/87, cooperating to provide fastresponse while controlling poppet 5145, 14, DIG. 5 oscillation. Thedamped member includes a spring within a hydraulic dashpot and serves asa reaction seat for the un- [56] References (med damped member. Fastpressure increases compress only the UNITED STATES PATENTS undampedmember while longer duration pressure signals will 898,659 9/1908 Kuehll37/DIG.5 also wmpressthc mp d member.

IO) IZX MN I I\ I3 P I T mnv 23 IHYI I 3. 6 21 ,8 7 5 INVENTOR. FRANK N.ALEXANDER 1 PRESSURE-ACTUATED VALVE This invention relates topressure-actuated fluid flow control valves and relates moreparticularly to improved biasing means providing improved performancecharacteristics for such valves.

Flow control valves of the pressure relief type are actuated in responseto a predetermined increase in hydraulic pressure to regulate andmaintain system pressure of a desired level. As is well known, suchvalves generally include a control member or poppet variably positionedby a hydraulic actuating pressure to meter, control and direct fluidflow to a low pressure outlet. Biasing means act against the controlmember in opposition to the pressure forces so that the control memberis positioned by the balance between the force exerted by hydraulicpressure and the biasing means. A problem common to such control valvesis obtaining proper response to the pressure actuating force to producethe desired control of fluid. Improper action of the control member,such as too slow or too fast responsive movement to the pressureapplied, may result in uncontrolled oscillation, chatter, excessive flowand pressure fluctuations and generally unacceptable performance. Bycorrectly damping movement of the control member, proper and acceptableperformance of the control valve can be achieved.

The present invention is directed toward an improved biasing memberconstruction for pressure actuated valves providing improved damping andgenerally better valve performance characteristics. The improved dampingcharacteristics produce stable operation, fast response and reduceoperational noise of the valve without introducing sluggishness orinsensitivity in its operation.

The invention contemplates at least a two-stage resilient biasing memberwithin the valve arranged to exert a biasing closing force on thecontrol member or poppet. One stage of the biasing member is dampedwhile the other is undamped. Compression of the damped stage requireslonger duration pressure signals, while the other undamped stage iscapable of moving quickly in response to pressure surges acting on thecontrol member.

In the preferred embodiment, a relief valve is provided with two springswhich are compactly arranged with the damped spring acting through andwith the undamped spring to bias the control member to a closedposition. Movement of the control member through pressure actuationsequentially causes compression of the undamped spring and then thedamped spring. The damped spring acts as the seat or reaction member tothe undamped spring during its compression. Damping of the one spring isachieved through the use of a hydraulic dashpot.

A primary advantage of my invention resides in providing a relief valvewhich retains the responsiveness of a valve having undamped biasingwhile eliminating the instability normally associated with undampedbiasing means. The valve of the present invention has particularapplication in systems where the exhaust or discharge is at somepredetermined back pressure above atmospheric. These advantages areachieved while still retaining a flat pressure versus flowcharacteristic desirable in such valves.

Further advantages and features of the invention are set forth in thefollowing detailed description and accompanying drawing which is alongitudinal section of a fluid pressure relief valve embodying theinvention.

More particularly, the drawing illustrates a portion of a fluid pressuredevice having a high pressure chamber 11 and a low pressure fluid returnchamber 12 communicating with a reservoir of low pressure fluid. Forexample, 10 may be a portion of a control valve having supply duct 11and return passageway 12. Cartridge-type relief valve 13 embodying thepresent invention is threadably secured to the device 10 and extendsthrough bore 14 to hydraulically communicate with chambers 11 and 12 andfunctions to selectively divert fluid from chamber 11 to chamber 12 andprevent overpressurization ofchamber l1.

Relief valve 13 has a two-piece housing including casing 15 whichreceives closure member 16. Interior bores 17 and 18 are provided inmembers 15 and 16, respectively. Cross bores 19 and 20 in valve housingsections 15 and 16 are open to the high and low pressure chambers 11 and12, respectively, and serve as inlet and outlet openings through thevalve. Held within closure 16 by snap ring 21 is seat 22 which is boredto sealingly receive the frustoconical outer surface 27 of poppet 23 inthe valve closed position as illustrated. Poppet 23 is movable withininternal bore 17 of member 16 and has a central bore 24 extendingthrough the poppet. The left end of poppet 23 is provided with outletopenings 25 which place bores 24 and 18 incommunication and permitselective communication between chambers 11 and 12 through bore 24 andopening 25. Appropriate sealing members 26 retard leakage from chamber11.

The outer portion of conical face 27 of poppet 23 is exposed to theassociated pressure in chamber 11 through passage 19. Sufiicient imposedpressure tends to urge the poppet leftwardly away from seat 22 to anopen position permitting fluid flow to be relieved from passage 19through bore 24 to low pressure chamber 12. This hydraulic opening forceis opposed by the biasing means, designated generally at 28, contactingthe poppet to urge it to the closed seating position.

The improved biasing means 28 of the present invention comprise twohelical compression springs 29 and 30 situated in passage 18 andsequentially arranged to extend between the closed end of cartridge 15and poppet 23. lnteriorly located pin 31 having an enlarged diameterflange 32 is interposed between the springs, and a conically ended bodyportion extends forwardly toward poppet 23. The conical end on pin 31acts as a flow deflector to assist and redirect fluid flowing fromchamber 11 axially through bore 24, outwardly through the coils ofspring 29, which compresses and reduces flow area as the poppet opens,and notches 25 to crossbores 20 and chamber 12.

Flange 32 is circular conforming to bore 18 and defines at itsperiphery, in cooperation with the internal diameter of bore 18, anannular restriction at 35. Two variable volume fluid chambers 33 and 34are in communication through restricted passage 35 formed between flange32 and the wall of bore 18. A suflicient number of outlet apertures 20are included in cartridge 15 so that chamber 33 openly communicates withlow pressure passage 12. On the other hand, fluid can escape fromchamber 34 only through annular restriction 35, thereby creating ahydraulic damping chamber or dashpot 34 limiting the speed ofcompression of spring 30 and speed of movement of poppet 23. Annularrestriction 35 is sized to provide the desired damping characteristicsand speed of movement of poppet 23. The restricted hydrauliccommunication between chambers 33 and 34 can be provided through otherconstructions such as one or more properly sized orifice holes extendingthrough pin 31, or orifices directly communicating chamber 34 with lowpressure passage 12.

In the closed position shown, springs 29 and 30 are set to apredetermined compression by inclusion of one or more shims 36 toestablish the desired closing bias force upon poppet 23. As pressure inchamber 11 reaches the predetermined limit, the force exerted on poppet23 overcomes the bias of springs 29 and 30 and moves the poppetleftwardly individually, an open position. Initially, spring 29compresses slightly against flange 32 as the dashpot chamber 34 preventssudden and immediate compression of spring 30. Alone, spring 29 exhibitsa relatively high spring gradient due to its relatively short length(that is, a closing force increasing very rapidly with springcompression) so that this initial movement, and the consequent flowrelieved from chamber 11, is limited. If the excessive pressurecontinues to be applied against poppet 23, fluid in chamber 34 is givensufficient time to flow through restriction 35 to undamped chamber 33and low pressure chamber 12, allowing spring 30 to compress and flange32 to move leftwardly. Moving together, the separate springs of biasingmeans 28 exhibit a lower gradient than either spring 29 or 30individually, the gradient of biasing means 28 being approximatelyequivalent to that of a single spring of equal length. As a result,poppet 23 in a normal manner continues to open as far as necessary torelieve sufficient flow from chamber 11 to limit pressure therein, thiscontinued poppet movement being damped and governed by fluid flow out ofdashpot chamber 34.

Consequently, the spring biasing and damping means permit rapid, butlimited, undamped movement of the poppet control member as well as ahydraulically damped and well controlled major opening response ofpoppet 23. The damping afforded by chamber 34 and the dual springarrangement permits valve 13 to relieve large flows from chamber 11without inducing poppet instability, pressure overshoot and oscillationand attendant disadvantages typical of underdamped valves. The dampingcreates smoother, quieter operation, eliminates poppet chatter, reducesvibration and generally improves the valve operation and life.

The quick opening feature of this valve is particularly adapted toinstant response to sudden, but brief, pressure surges and shocksexperienced in chamber 11. In such instances, spring 29 compressesslightly against flange 32 and permits a limited flow out of chamber 11and allows poppet 23 to quickly return to the closed position aspressure in chamber 11 is relieved. Such operation is distinctlyadvantageous over previous designs where such pressure surges createdimproper poppet response. Prior valves, having damping characteristicssimilar to that exhibited by the present valve during compression ofspring 30, would be so slowly responsive that the poppet would not reactat all to the momentary pressure surge, resulting in excessively highpressure peaks and accompanying stress upon the pressure system. On theother hand, previous valves designed to respond to such pressure surgeshave inherently been underdamped and unstable; when responding to normalpressure forces and not to surges, the poppet would move open too far,relieve too much fluid and cause consequent drop in pressure in chamber.Such action in many instances induced oscillation of the poppet member.The present valve, however, provides quick opening to prevent highpressure peaks in chamber 11 without inducing poppet oscillation andchatter.

lt can thus be seen that the present invention provides a novel biasingmeans that is provided with intermediate damping staging the biasingeffect. The one stage is undamped and sensitive to high frequencymovements while the damped stage is sensitive to lower frequency, longerduration poppet movements. Such biasing more nearly matches therequirements of pressure chamber 11 and reduces poppet chatter andunwanted oscillation.

The present invention has been found capable of being incorporated instandard valves to replace a conventional singlespring bias, since thelength of springs 29 and 30 together are approximately equivalent to thelength ofa corresponding single spring. This is due to the sequentialarrangement of springs 29 and 30 whereby both are compressed to providethe control member biasing force. In fact, it has been found suitable incertain valves to split an existing spring into two sections, a smallersection 29 and larger section 30 to produce the improved biasingmembers.

To prove the effectiveness of the improved relief valve design, a valveaccording to the invention was designed and tested in comparison to aconventional valve identical in design save for a conventional singlespring biasing means. The conventional valve had excellent responsecharacteristics to shock loading as determined by a very low peakpressure overshoot, about 2,000 p.s.i. peak pressure when adjusted tocrack" or open at 1,750 p.s.i. As inherent to many such fast responsevalves, the conventional valve was underdamped and oscillated creatingexcessive wear and undue noise. This was reflected in the wide band ofpressure variation, about 1,000 p.s.i., occurring in the high pressurechamber.

The improved valve incorporated helical coil springs 29 and 30, bothhaving a wire diameter ofO. 103 inches. Spring 30 had a spring rate of772 pounds/inch and was 0.780 inches long, while spring was 0.615 incheslong having a spring rate of 1,080 pounds/inch. Bore 18 was nominally0.519 inches in diameter with circular flange 32 being nominally 0.512inches leaving an annular restricted passage 35 of 0.07 inches in width.In the test, the relief valve was installed and adjusted so that 1,750p.s.i. opening pressure force in chamber 11 was required to crack" thepoppet open with a back pressure of p.s.i. being maintained in exhaustchamber 12 by an appropriate needle valve. Pressure in chamber 11 wascontinually monitored as a shock load having a pressure rate of about100,000 p.s.i./second was created in chamber 11. Upon opening inresponse to the shock loading, my improved valve maintained a variationin pressure in chamber 11 of only about 250 p.s.i. with a peak pressureofabout 2,000 p.s.i., substantially duplicating the fast responseperformance of the conventional valve under the same conditions. Theincreased stability, as evidenced by the reduced pressure fluctuation,eliminated the poppet chatter, oscillation and excessive operationalnoise prevalent in operation of the conventional valve. Thus, the testillustrated the effectiveness of this invention in providing adequatedamping for a fast response valve without introducing sluggishness orincreasing pressure peaks and overshoot.

The invention has been specifically shown and described as it isincorporated in a high pressure relief valve to provide proper dampingwithout introducing sluggishness or insensitivity to its operation. Theinvention may be similarly utilized in other types of pressure-actuated,spring-biased valves, and accordingly, the foregoing specification is tobe considered exemplary in nature and not limiting to the scope andspirit of the invention as set forth in the appendaged claims.

lclaim:

l. A fluid relief valve comprising:

a. a body member defining a chamber therein and having an outlet andinlet, said body adapted to be connected to a housing with said inletbeing exposed to fluid at high pressure,

b. an interior seat within said chamber,

c. an axially movable pressure-responsive poppet in said chamber, saidpoppet in a closed position abutting against said seat and adapted tomove away from said seat upon establishing predetermined high pressureat said inlet thereby placing said inlet and outlet in hydrauliccommunication; and

d. biasing means in said chamber urging said poppet to a normally closedposition, said biasing means being comprised of an undamped member and adamped member, said undamped member being responsive to initialapplication of predetennined pressure to permit limited undamped openingofsaid poppet and said damped member being responsive to continuedapplication of said predetennined pressure to permit further dampedopening of poppet thereby substantially reducing instability of saidvalve.

2. The relief valve of claim 1 wherein said first and second members ofsaid biasing means comprise helical compression springs.

3. The relief valve of claim 1 wherein said first and second members ofsaid biasing means comprise compression springs separated by a slidablepartition dividing the chamber into first and second fluid chambersrespectively containing said first and second biasing means, saidpartition adapted to restrict fluid flow from said first chamber wherebycompression ofsaid first biasing means is hydraulically damped.

4. A fluid relief valve comprising:

a. a body member defining a chamber therein and having an outlet andinlet communicating with said chamber, said body adapted to be connectedto a housing with said inlet being exposed to fluid at high pressure,

b. an annular interior seat within said chamber,

c. an axially movable pressure-responsive poppet in said chamber havinga passageway therein coaxial with said bore, said poppet in a closedposition abutting against said seat and adapted to move away from saidseat upon establishing predetermined high pressure at said inlet therebyplacing said inlet and outlet in hydraulic communication through saidpassageway, and

biasing means extending between said body and said poppet urging saidpoppet to a normally closed position, said biasing means being comprisedof a damped member adjacent said body member and an undamped memberadjacent said poppet, said undamped member being initially responsive toinitial application of predeten'nined pressure to permit movement saidpoppet from said seat and said damped member being responsive tocontinued application of predetermined pressure whereby both saidmembers sequentially compress to permit further opening of said poppetthereby substantially reducing instability of said valve.

5. A pressure relief valve comprising:

a. a housing member defining a central chamber closed at one end andhaving a fluid inlet communicating with said bore and a fluid outletcommunicating with said bore intermediate the inlet and said closed end,

b. a poppet member movably disposed in said bore and cooperating with aseat to control flow therethrough from the inlet to the outlet, saidpoppet having a surface portion arranged whereby predetermined fluidpressure associated with the inlet exerts an opening force on saidpoppet urging same to an open position permitting flow from the inlet tothe outlet,

0. a divider plate in said bore intermediate said closed end and saidpoppet closely cooperating with the bore wall to define in said borefirst and second fluid chambers respectively extending axially from theclosed end to said plate and from said plate to said poppet, said secondchamber being in open communication with said outlet, d. flowrestriction means permitting restricted fluid flow from the first to thesecond chamber,

first resilient means arranged in said first chamber between the closedend and dividing plate, and

f. second resilient means spring in said second chamber extendingbetween said damping plate and said poppet, said first and secondresilient means exerting a biasing force on the poppet to urge same to anormally closed flowblocking position and normally cooperativelycompressing upon actuation of the poppet by sufficient inlet pressurewherein poppet movement is hydraulically damped and whereby said secondresilient means is capable of limited compression against said dampingplate independent of first spring compression to permit undamped openingmovement of said poppet.

6. The relief valve of claim 5 wherein said flow restriction means areformed as an annular restriction defined by said chamber and theperiphery of said divider plate.

7. The relief valve of claim 5 wherein said damping plate includes aprotuberant portion extending axially into said second chamber towardsaid poppet and having a conically formed end for diverting axiallydirected fluid flow from the inlet through said poppet central boreradially outwardly toward said outlet.

1. A fluid relief valve comprising: a. a body member defining a chambertherein and having an outlet and inlet, said body adapted to beconnected to a housing with said inlet being exposed to fluid at highpressure, b. an interior seat within said chamber, c. an axially movablepressure-responsive poppet in said chamber, said poppet in a closedposition abutting against said seat and adapTed to move away from saidseat upon establishing predetermined high pressure at said inlet therebyplacing said inlet and outlet in hydraulic communication; and d. biasingmeans in said chamber urging said poppet to a normally closed position,said biasing means being comprised of an undamped member and a dampedmember, said undamped member being responsive to initial application ofpredetermined pressure to permit limited undamped opening of said poppetand said damped member being responsive to continued application of saidpredetermined pressure to permit further damped opening of poppetthereby substantially reducing instability of said valve.
 2. The reliefvalve of claim 1 wherein said first and second members of said biasingmeans comprise helical compression springs.
 3. The relief valve of claim1 wherein said first and second members of said biasing means comprisecompression springs separated by a slidable partition dividing thechamber into first and second fluid chambers respectively containingsaid first and second biasing means, said partition adapted to restrictfluid flow from said first chamber whereby compression of said firstbiasing means is hydraulically damped.
 4. A fluid relief valvecomprising: a. a body member defining a chamber therein and having anoutlet and inlet communicating with said chamber, said body adapted tobe connected to a housing with said inlet being exposed to fluid at highpressure, b. an annular interior seat within said chamber, c. an axiallymovable pressure-responsive poppet in said chamber having a passagewaytherein coaxial with said bore, said poppet in a closed positionabutting against said seat and adapted to move away from said seat uponestablishing predetermined high pressure at said inlet thereby placingsaid inlet and outlet in hydraulic communication through saidpassageway, and d. biasing means extending between said body and saidpoppet urging said poppet to a normally closed position, said biasingmeans being comprised of a damped member adjacent said body member andan undamped member adjacent said poppet, said undamped member beinginitially responsive to initial application of predetermined pressure topermit movement said poppet from said seat and said damped member beingresponsive to continued application of predetermined pressure wherebyboth said members sequentially compress to permit further opening ofsaid poppet thereby substantially reducing instability of said valve. 5.A pressure relief valve comprising: a. a housing member defining acentral chamber closed at one end and having a fluid inlet communicatingwith said bore and a fluid outlet communicating with said boreintermediate the inlet and said closed end, b. a poppet member movablydisposed in said bore and cooperating with a seat to control flowtherethrough from the inlet to the outlet, said poppet having a surfaceportion arranged whereby predetermined fluid pressure associated withthe inlet exerts an opening force on said poppet urging same to an openposition permitting flow from the inlet to the outlet, c. a dividerplate in said bore intermediate said closed end and said poppet closelycooperating with the bore wall to define in said bore first and secondfluid chambers respectively extending axially from the closed end tosaid plate and from said plate to said poppet, said second chamber beingin open communication with said outlet, d. flow restriction meanspermitting restricted fluid flow from the first to the second chamber,e. first resilient means arranged in said first chamber between theclosed end and dividing plate, and f. second resilient means spring insaid second chamber extending between said damping plate and saidpoppet, said first and second resilient means exerting a biasing forceon the poppet to urge same to a normally closed flow-blocking positionand normally cooperatively compressing upon actuation of the poppet bysufficient inlet pressure wherein popPet movement is hydraulicallydamped and whereby said second resilient means is capable of limitedcompression against said damping plate independent of first springcompression to permit undamped opening movement of said poppet.
 6. Therelief valve of claim 5 wherein said flow restriction means are formedas an annular restriction defined by said chamber and the periphery ofsaid divider plate.
 7. The relief valve of claim 5 wherein said dampingplate includes a protuberant portion extending axially into said secondchamber toward said poppet and having a conically formed end fordiverting axially directed fluid flow from the inlet through said poppetcentral bore radially outwardly toward said outlet.